Liquid Crystal (LC) lenses and other liquid crystal optical devices are known in the art. One geometry is a layered planar construction in which a liquid crystal layer is held in a cell between glass or plastic plates. An electrically variable gradient index (so called GRIN) lens can be formed by controlling the relative orientation of liquid crystal molecules to create a spatial variation of the index of refraction of the liquid crystal material within an aperture of the device. FIG. 1 illustrates a space modulated director variation across an optical aperture of a LC lens optical device. Z is the optical axis of the LC lens optical device along which incident light propagates. Such a lens is known from U.S. Pat. No. 8,033,054 issued Oct. 11, 2011 to Galstian et al. which is incorporated herein by reference. Because the ordered nematic liquid crystal causes the light to be split into two polarizations, a single layer of liquid crystal can focus only a single polarization. Two layers of liquid crystal provided in proximity to each other provide a natural or unpolarized light image onto an image sensor. Electrically controlled liquid crystal lenses made according to the principles of U.S. Pat. No. 8,033,054 are commercially available from LensVector, Inc. and provide good optical power tunability and lens quality, particularly for small aperture lenses of about 3 mm diameter.
Various medical conditions are addressed by fitting an eye with intraocular lens prostheses to replace a natural crystalline lens of the eye. Such medical conditions include aging effects, or can result from accidents or from exposure to atypical environmental conditions.
For example, development of a cataract is a common condition experienced with age. The eye is typically fitted with an intraocular lens prosthesis during cataract surgery. A goal of cataract surgery has long been to provide, postoperatively, unaided (without wearing glasses) high-quality distance, intermediate, and near vision. The use of a tunable liquid crystal lens as an intraocular prosthesis is being proposed herein.
For many years, basic attempts to restore vision have included surgically empting a capsular bag in which the natural crystalline lens of the eye resides and refilling the capsular bag with an accommodating polymer which matches the behavior of a juvenile lens. While such attempts have received considerable attention, an effective actualization remains elusive today in part because properties of homogeneous polymers are insufficient to mimic properties of an inhomogeneous natural crystalline lens. Emptying the capsular bag may induce some damage to tissues other than the crystalline lens. As well, any crystalline lens characterization is necessarily performed on an imperfect lens slated for invasive medical removal with the desire of providing a perfect intraocular prosthesis postoperatively. Even if a characterization of the crystalline lens from an earlier age would have been available, the surrounding tissues also change with age rendering such characterization insufficient.
Implanting a fixed focus (monofocal) lens has been attempted in the prior art with limited degree of success. Postoperatively the combination of the remaining adjoining tissues and a fixed focus lens provide a limited degree of accommodation (controlled focus variability range) compared to the juvenile natural lens. Such monofocal prosthesis combinations may only provide between 0.5 to 1.5 diopter pseudoaccommodation after surgery. In comparison, research by Mitchell Scheiman and Bruce Wick in Clinical Management of Binocular Vision, Lippincott, N.Y., 1994 suggests that on average a juvenile lens provides 18 diopters variability in average amplitude of accommodation. The average amplitude of accommodation at a given age may be estimated by Hofstetter's formula: 18.5 minus one third of the patient's age in years.
Also considered insufficient are single optic flexible prostheses which fill the entire capsular bag and remain stationary while changing an anterior/posterior dimension to vary optical power subject to forces provided by the ciliary body. Some attempts suffer from material incompatibilities while others remain theoretical.
Dual optic prostheses have been implanted, however suffer from low optical power in the range of 2.5 diopters.
While such prior art intraocular implants may provide clearer vision after an operation, the limited degree of post operative accommodation requires additional visual aids such as glasses or contact lenses.
Recently tunable Liquid Crystal (LC) lenses have been proposed for use in active accommodation. With an appropriate geometry, a variety of optical components employing LC optical devices can be manufactured, for example: a lens, a corrective optical element, an optical shutter, iris, etc. LC lenses provide significant advantages being thin and compact. The optical power of a LC lens refers to the amount of ray bending that the LC lens imparts to incident light (and more specifically to an incident light image field representative of a scene) passing therethrough.
For example, in co-pending, commonly assigned patent application U.S. Ser. No. 13/369,806 entitled “Tunable Liquid Crystal Lens Intraocular Implant and Methods Therefor”, claiming priority from U.S. 61/441,863 of same title filed Feb. 11, 2011, the entireties of which are incorporated herein by reference, an intraocular adaptive lens prosthesis apparatus is described. A tunable liquid crystal lens is driven in response to a stimulus signal to provide accommodation. In some implementations the apparatus includes a tunable liquid crystal lens encapsulated in the intraocular prosthesis with control electronics and a power source. In other implementations the apparatus includes a tunable liquid crystal lens encapsulated in the intraocular prosthesis with a control signal receiver while an external control electronics package transmits the control signal. In some embodiments the tunable liquid crystal device corrects visual shortcomings of the natural eye.